Hoping I'm right, but there's no other person (Youmu) to be seen.
Just Yuyuko and maybe Youmu's ghost half.
She is mentioned in the commentary, but just that.

Edit: So my screen was too bright and didn't see the shadow. My very bad, sorry about that.

Gekiro said:

...So my screen was too bright and didn't see the shadow. My very bad, sorry about that.

@Gekiro, that's totally fine. Let's leave it at that.

Precious.